Electron microscope



June 27, 1950 J. E. LE POOLE ET AL ELECTRON-MICROSCOPE Filed Aug. 6,1947 i5 Z5 -Z INVENTORS.

I MMIII/3111001115 @www I/.ERHUEFF Patented June 27, 1950 UNITED s"PATENTI OFFICE. nLEo'rn(it5 1'lll-i0SCOIEv v vv i v Jan Bart Le Poolekand Adrianus Verhoe, Eindhoven, Netherlands, vassignors to HartfordNational Bank and- Trust Conn., as trustee Company, Hartford,

Applieationnugust s, 1947, serial N0. 766,792 l In the NetherlandsAugust 30, 1946 i s claims.'

The invention relates "to electron microscopes and more'particularlyl to'an electron microscope 'It is an object of the present invention toprovide `a nev.rr and novel specimen-holder arrangement for an electronmicroscope.

It is another object of the invention rto provide a specimen-holderarrangement whichvvill permit a rapid and easy change of specimens bysimple manipulations.

It is a further object of the invention to provide a specimen holderarrangement Which will permit change of specimens While maintaining ahigh degreeof vacuum in the vacuum chamv ber.

closed by. a stopper which carries the objectl holder; Along the lWallof this tube are provided diametricaliapertures through which theelectron beam of the microscope may pass inl a given position ofthetube. from the given position these apertures are hermetically closed bymeans of a solid body bearing against the tube at the apertures.

AccordingI tothe invention,v the removal of the `object-holder whichsupports the specimen to be examined, is onli7 possible vwhen theA tube'occupies 'a position in which the diametrical a'pertures'iprovided topermit the passage of the electron `'beams are closed. Thus protectionagainst ingress of air to the vacuum chamber during the change ofspecimensis obtained. Accordingly, When the tube is so positioned thestopper may be Withdrawnin the direction of (ol. 25o-49.5)

vided whichv locks the said handle in an open n position, aposition inwhich the beam apertures When the tube is rotated f 130) 'with respectto thetube.

are so placed that the electron beam passes through the specimen or theobject holder. A turn of the bayonet then permitsclosing of theyapertures thus preventing passage of the electron beam.

It may be desirable in some circumstances to be able to displace theobject slightly without immediately moving the beamapertures out of the`axispof lthe microscope, fory it is sometimes desired to cause theelectron beam to -fall on the object inL different directions, forexample, when making stereoscopic exposures. It

istherefore advantageous ,that the handlehave a' certain freedom ofAmovement (for example According to theinvention it is also possible toobtain 'a good seal between thetubeand the vacuum chamber by means lofvalvesmade of rollers which resiliently bear against the tube and theaxes of which rollers are parallel to the tube axis.- Notwithstandingthe spring pressure required for closing the beam apertures when usingthese rollers very little frictional resistance isjexperienced when thetube` isturned since the rollers are rotatable about their yonly axes.Perh fect sealing is ensured in this case if the rollers are made ofelastic material` such as rubber. Unfortunately the useof rubber entailsthe. disadvantage of Wear Whichmakes an exchange of rollers necessaryyfrom time to time. Moreover, the specimen under ,observation isVIlikely to become contaminated by scraps of material ground off therollers. According tothe invention, rthis disadvantage may be obviatedby mounting the rollers `on metal `spindles and by giving the tube aprolesuch thatl in the openposition .when the electron` beam may throughthe aperl tures these spindles bear against the tube and the rollersare-clear thereofyvhereas in the closed position in which passage of theelectron beam is lpreventedthe spindles are positioned in depressions ofthe tube and the .rollers are pressed against the apertures to. closethem. f

. The invention will` be explained more fully with reference to theaccompanyingy .drawing whereiny v l .Fig 1 diagrammatically represents,byA way of example, oneembodirnent of the sluicing de,- viee in anelectron microscope. v Figs. 2, 3, and 4 showy-a further embodiment ofsuch a-.device accordingl to thev invention. n.

p Fig. 1 is a v.cross-sectional view ,through .the

axis ofy theelectron,l microscope and represents a small portion of thedischarge vessel which,

in the neighborhood of the sluicing device, has

is rotatable about its axis 3 which intersects the axisv 4 of thedischarge vesselat right angles.

In order to facilitate ,this rotation the tube is provided with a handwheel 5.

The tube is closed by a stopper having secured to it an object-holder 'Iwhich extends, within the tube 2 over a, length such that' the specimen8 provided at the end of the holder is located in the centrally 'passingelectron beam. In the wall of. the tube 2, in alignment with theaxis/'4, two diametrical aper tures 9 and I0 are provided which allowthe electron beam to pass through the tube.wal1'.A

metal body I I secured tothe wall I and having provided in its aperturesI2 and I2a correspond` ing with the apertures 9 and I0 of the tube, andyth'etube itself formtogether a plug cock. `Her metical sealing may befavoured by providing on the tube a thin layer of the packing materialknown under the name of cockfat `When a specimen is to be removed fromthe micrscope itis necessary to turn the tube 2 a quarter of a turn withthe aid of the. handwheel -5, in which event the apertures 9 and I0 areclosed bythe solid portion of metal body I I so that the` electron beamis prevented from penetrating through the wall of the `tube 2 into thelower vsection discharge vessel, penetration of f air' through thesebeam apertures 9 and I8 into the` lower section of the vessel being madeimpossible at the same time. Without any'objectionable result thestopper 6 may then be taken from the tube and with itvthe object holder'I and the specimen 8 are removed.l After'the stopper '6 'has beenreplaced upon the tube 2 lthe latter may be moved again into' itsprevious position in 'which the apertures 9 and I0 are located inalignment with the apertures I2 and I2a and the object istr'ansradiatedv by the electron beam. The rair which, after the removalof the stopper 6 entered thetube 2 to llit may now pass throughkvtheapertures 9 and III into the discharge vessel,

thisquantity beingQhowever. so small that it may easily be removedwithin an extremely short tinrle by an 'exhausting ydevice which ispermanently connected to the discharge vessel.

i With'a device constructed in accordance with c '2' and 3 the quantityof airlwhich may leak v into the vessel during the change of specimensis even less than in the aforementioned construction. In this embodimentthe object-holder I8 has ra diameter'lwhich is substantially equalto theinternal diameter of the tube I3 so that the I interior of thel tube I3is lled for the major vpart and there remains only little space for airleakageinto the vessel. c c In this embodiment the sluicing device isprovided on a partition of a metal portion of the wall fof dischargevessel as shown more clearly in Fig. 3. Fig. 2r is a cross-section ofthe vessel taken through a thicker portion `of this partition' and'Fig.'3 is a cross-sectional view in a plane passing through the axisperpendicular to the object-holder. Fig. 4 shows in a perspective lview, on a rlarger scale,l a detail of a bayonetl ma metarwau vIt. Thetube itself is.A eiosesby means of a stufling box IS'throu'ghwhichpasses vided in the form of hooks and 2I gripping Abehind a rim 22 ofthe knob I9 prevents the `withdrawal of the object-holder orlspecimenholder I8. When the knob I9 is turned a pin 23-secured to thetube I3 and passing through the knob I9 is carried along with it withthe result that the tube I3 is rotated about its axis. The knob aperturethrough which the pin 23 passes Yhas an elongated shape so that the pinthrough a certain'vangle.

has a certain freedom of movement and the object holder can be turnedwithin the tube I3 This is desirable for the making of stereoscopingexposures or if for other reasons itis desired to Vcause the electronbeam to fall on the object at diierent angles. l

' If, after the pin 23 has been engaged, the knob YIIE is -furtherrotated, the hooks 20 vand 2I slide over the rim 22 and after a rotationthrough an angle oi' approximately 90 they will belocated'behindrecesses provided in the rim 22 (see Fig. 4) The hooks'ZIland 2| now no longer prevent the object holder I 8 from being removed,in which event the tube II3 itself is held in place since it is retainedby screws 24 whose ends engage a circular groove in the outer wall ofthe tube. However, due to the rotation` of the tube and the valve actionto 'be' described below, the direct communication between the interiorof the tube and the dischargevessel has Abeeninterrupted.

The valve action is effected by valves in the form of rollers 21 and 28mounted onI spindles 29 and 30 which are pressed'towards'the tube I3by'springs 3I and 32. .These rollers serve to close the beam apertures25 and 26 of' the tube I3. If, as shown in Figs. 2 and 3, the tube I3has been turned so that the'beam apertures lie in the axis of'thedischarge vessel, the rollers 2l and 28are clear^of the tube since asmay be 'seen in the cross-section taken through thebeam apertures thetube has a reduced external diameter so that solely the spindles bearagainst the tube.

they beam apertures the outer surface ofthe tube --not subject to wearand the specimen 35'seu maybe seen to exhibit depressions 33 and 34 atthe points at which, after rotation, the ends of the' spindlesv 29 and3U will be located. kIf consequently the tube I3 is rotated `from theposition shown in Fig. `2` the spindles 29 and 30 are lowered into thedepressions land the rollers 2'I and 28 engage the tube; thushermetcally closing the apertures 25 and 26. The spindles 29 and 30consist' of metal whereas, in order to ensure a completely vacuum-tightsea1 the'rollers -21 and 28 are made of rubber or similar elasticmaterial. Since the rollers are normally'clear ofthe tube and arepressed thereon onlyin the closed position Vof the tube they aresubstantially cured to the holder I8 remains free from impurities whichotherwise might bev present due to this wear. f.

In order to be able to easily ascertain in darkf ness thepositionoccupiedby the specimen, the

knob I9 is providedwith a rib36in such manner that in the mid-positionof the object-holder it is, with respect to the tube in alignment withthe pin 23'passing through the knob. Thus'it In the longitudinal sectiontaken through is possible by touch to determine the position of thespecimen within the tube.

What we claim is:

1. An electron microscope comprising a discharge vessel, a tube with aclosed bottom extending into said vessel and intersecting the axisthereof, said tube being hermetically sealed to said vessel and havingapertures for the passage of the electron beam, means for rotating saidtube from the outside, an exchangeable carrier arranged in said tube andadapted to support a specimen for observation through said beamaperture, a member for closing said tube and supporting said specimencarrier, and means for closing said beam apertures when said tube isrotated to a position in which said tube closing member is ready forremoval.

2. An electron microscope comprising a discharge vessel, a tube with aclosed bottom extending into said vessel and intersecting the axisthereof at right angles, said tube being hermetically sealed to saidvessel and having apertures for the passage of the electron beam, meansfor rotating said tube from the outside, an exchangeable carrierarranged in said tube and adapted to support a specimen for observationthrough said beam apertures, a stopper for closing said tube andsupporting said specimen carrier, and a solid body bearing against thetube for closing said beam apertures when said tube is rotated to aposition in which said tube closing member is ready for removal. y

3. An electron microscope as claimed in claim 1, comprising a lockingmeans for securing said tube closing member while the beam apertures arein open position.

4. An electron microscope comprising a discharge vessel, a tube with aclosed bottom extending into said vessel and intersecting the axisthereof at right angles, said tube being hermetically sealed to saidvessel and having apertures for the passage of the electron beam, anexchangeable carrier arranged in said tube and adapted to support aspecimen for observation through said beam apertures, a stopper forclosing said tube and supporting said specimen carrier, a handle adaptedto rotate the tube and to lift the specimen carrier out of said tube, abayonet locking device for securing the handle against withdrawal whilethe beam apertures are in open position, and means for closing the beamfio apertures when upon rotation of the tube the handle becomes unlockedand ready for withdrawal.

5. An electron microscope as claimed in claim 4, wherein said handle hasan elongated arcuate slot and wherein a pin is secured to said tube andslidably received in the slot in said handle, whereby the handlereceives a certain freedom of angular movement with respect to said tubeand the specimen can be placed at different angles with respect to theelectron beam.

6. An electron microscope as claimed in claim 4, wherein said handle hasan arcuate slot of about 30 degrees and wherein said tube has a pinsecured thereto, said pin being slidably received in said slot, wherebythe handle is free to move for said 30 degrees with respect to said tubeand the specimen can be placed at different angles with respect to theelectron beam.

7. An electron microscope comprising a discharge vessel, a tube with aclosed bottom extending into said vessel and intersecting the axisthereof, said tube being hermetically sealed to said Vvessel and havingapertures for the passage of the electron beam, means for rotating saidtube from the outside, an exchangeable carrier arranged in said tube andadapted to support a specimen for observation through said beamapertures, a member for closing said tube and supporting said specimencarrier, and valves for closing said beam apertures when said tube isrotated to a position in which said tube closing member is ready forremoval, said valves being in the shape of rollers adapted to bearresiliently against said tube.

8. An electron microscope comprising a dis charge Vessel, a tube with aclosed bottom extending into said vessel and intersecting the axisthereof, said tube being hermetically sealed to said vessel and havingapertures for the passage of the electron beam, means for rotating saidtube from the outside, an exchangeable carrier arranged in said tube andadapted to support a specimen for observation through said beamapertures, a member for closing said tube and supporting said specimencarrier, and valves for closing said beam apertures, said valvesconsisting of rubber rollers having their axes parallel to the tube axisand being adapted to engage with recesses formed on the outer wall ofsaidtube, thereby closing said beam apertures when said tube is rotatedto a position in which said tube closing member is ready for removal.

9. An electron microscope comprising .a discharge vessel, a tube with aclosed bottom extending into said vessel and intersecting the axisthereof, said tube being hermetically sealed to said vessel and havingapertures for the passage of the electron beam, means for rotating saidtube from the outside, an exchangeable carrier arranged in said tube andadapted to support a specimen for observation through said beamREFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name- Date 2,264,210 Krause Nov. 25, 19412,420,561 Bachman May 13, 194

` FoREiGN PATENTS Number Country Date y 518,317 Great Britain Feb. 23,1940

